Two pipes A and B can fill a tank in 24 hours and 30 hours respectively

Two pipes A and B can fill a tank in 24 hours and 30 hours respectively. If both the pipes are opened simultaneously in the empty tank, how much time will be taken by them to fill it?
(a) 13 hour 20 min
(b) 12 hour 10 min
(c) 14 hour
(d) 10 hour 5 min